1. Field of the Invention
The present invention relates to a novel active motion and vibration damping arrangement and, in particular, pertains to an active vibration damping arrangement which is adapted to improve passenger ride comfort in various types and categories of transport vehicles; especially such as, but not limited to railroads, buses, automotive devices, maglev (magnetic levitation) vehicles, trains and people mover devices in general. In essence, pursuant to specific physical applications and uses, the inventive and uniquely employed active motion and vibration damping arrangement is intended to provide a suitable supplemental damping system installed in addition to currently employed so-called passive vibration dampers which are widely employed in connection with such vehicles, transportation devices, vibration-susceptive machinery and the like.
2. Discussion of the Prior Art
At the current time, most transportation systems comprising; for example, railway cars, buses, trucks, automobiles, maglev vehicles (of both the high and low speed type) and people movers (such as escalators or moving sidewalks) employ passive damping devices which ordinarily utilize mechanical and/or air springs in providing for their secondary suspension systems. Such passive damping devices are essentially adapted to attenuate high-frequency vibrations which are encountered; for example, such as are generally above 2 Hz, whereby such vibrations are generated and introduced into the vehicles or trains when these are traveling over irregularities; for example, those present in steel rails, guideways or rough roadways. These high-frequency vibratory disturbances are frequently attenuated by positioning a damper comprising a spring-mass combination between the car body and the passenger compartment floor of trains or vehicles, so as to form a suspension system. Although this is generally effective in attenuating or even eliminating high-frequency disturbances or vibrations, there is encountered the disadvantage of introducing low-frequency heave and sway motions into the passenger compartments of such vehicles. Frequently, such low-frequency vibrations or motions are physically acceptable to the vehicle or train passengers, but do not facilitate the ability of easily reading, writing or walking in the passenger cabin of the vehicle or train such as would be normally encountered with an airplane smoothly flying in calm air conditions. A drawback or limitation of passive dampers which are currently widely employed in this technology resides in that these dampers possess inherently low damping characteristics near the natural frequency of the spring/mass secondary suspension systems installed in the vehicles. For example, the usual damping factor for such suspension systems is approximately 0.3, whereas a value of about 0.8 would be more desirable, but is difficult to implement in a passive mechanical vibration and motion damping structure.
In order to improve upon the motion and vibration damping systems of the current technology, which, as indicated hereinabove, are primarily passive in nature, supplemental active motion damping systems have been proposed or utilized in lieu of such passive damping systems.
Thus, for instance, active vibration dampers with reactive force producing pistons are disclosed in Gossman et al. U.S. Pat. No. 5,332,203, wherein an active vibration damper which is effective in a simple direction or along one axis is positioned between an automotive engine and a chassis, and is adapted to be controlled by opposedly located force motors acting on a fluid piston arrangement responsive to an accelerometer. Such an active vibration damper may be utilized either alone or as a supplement to normally employed passive vibration damping arrangements or systems, such as springs and dashpot combinations, as is well known in the technology.
Schalz U.S. Pat. No. 5,086,564 discloses an active vibration damping device and method, whereby an active vibration and motion damper may be interposed near a first end of a beam and an actuator responsive to a control located near a second end of a beam so as to control vibrations acting in one direction.
Maichle U.S. Pat. No. 4,924,943 discloses an agricultural tractor or the like including an active vibration damper which may be utilized in conjunction with a passive damping system or spring/mass unit in order to attenuate vibration forces encountered by the tractor vehicle. The active vibration damper, which acts primarily in one direction, is employed also to dampen pitch vibrations of the vehicle when traveling on rough terrain and decrease adverse influences over the range in the driving characteristics of the vehicle.
Fedor U.S. Pat. No. 4,892,273 and Geohegan, Jr.. et al. U.S. Pat. No. 4,083,433 each disclose active vibration dampers, wherein Fedor is directed to damping vibrations in spacecraft structures and Geohegan, Jr. et al. is directed to primarily provide for signal processing in detecting undue vibrations in a drive unit.
The foregoing types of active vibration and motion damping systems and arrangements, although generally satisfactory within their particular functional parameters and specific physical utilizations; however, fail to provide for multi-axis active motion and vibration damping which is able to reduce to an appreciable extent or even completely attenuate or suppress motion and vibration effects in heaving and sway directions which are encountered by vehicles and other motive structures as described herein, and to increase, either independently or as a supplement to possible passive damping devices, the overall effective range in the damping of motions and vibrations over considerably broader frequency ranges and to thereby significantly decrease encountered disturbance levels in vehicular passenger compartments to acceptable values, thereby considerably enhancing passenger comfort while traveling in such vehicles or other types of conveyances.